1. Field of the Invention
The present invention relates to a needle-coupled parallel mechanism that performs an operation on a target object while controlling its position and posture in a three-dimensional space.
2. Description of the Related Art
In recent years, many medical devices have been developed for various medical purposes, for example, biopsy and drug infusion into living bodies. A typical example of such medical devices consists of a needle inserted into a living body to perform a medical function, such as drug infusion or tissue sampling, and a mechanism coupled to the needle to control the posture and position of the needle.
The size of and the precision in the working area of the medical device are important factors in determining the performance of the medical device. The size of the working area means the size of the area where the position and posture of the needle are controllable, and the precision in the working area means how precisely the needle is controlled in the working area. Since the position and posture of the needle are controlled by the mechanism, a broad working area and a high precision of the mechanism are also required in order to improve the performance of the medical device.
Serial mechanisms have been usually used in medical devices. Such a serial mechanism includes a plurality of links connected in series with each other. The serial mechanism has many problems despite the advantage of a broad working area. For example, the needle reflects cumulative errors generated in the respective links in the course of controlling the posture and position of a needle, resulting in a very low precision of the serial mechanism. Further, the links coupled in series inevitably increase the size and inertial mass of the serial mechanism, which greatly increases the force necessary to control the posture and position of the needle.
Thus, there is a need to develop a new type of mechanism that can control the posture and position of a needle with a small force while possessing a broad working area and a high precision.